The present invention relates to a lattice mast crane having a lattice mast boom which can be luffed up in a vertical luffing plane and which comprises a pivotal connection piece, a plurality of lattice pieces releasably connectable to one another, and a head piece, with the lattice mast boom having a two-strand or multi-strand region.
With such lattice mast cranes, the lattice mast boom can be transported to the deployment site dismantled into its individual components and can be assembled on site by connecting the individual lattice pieces to the pivotal connection piece and to the head piece. The boom of the lattice boom crane is pivotally connected about a horizontal luffing axis to the superstructure of the crane in the working state and can thus be luffed up in the vertically extending luffing plane.
The boom of this lattice mast crane is usually guyed by a guying rope arrangement and is held thereby on the luffing of the boom. With lattice mast booms, in contrast to non-guyed telescopic booms, it is therefore not the deflection of the boom in the luffing plane which is the decisive criterion for the peak payloads when lifting large loads in a steep position, but rather the lateral deformation perpendicular to the luffing plane. If the lattice mast boom undergoes a laterally acting force, e.g. by the power of the wind, the lifting of a load with the already present excursion effects a larger lateral torque.
In known lattice mast booms, the lattice mast is in this respect built up of the pivotal connection piece, a single strand of lattice pieces connected to one another and the head piece so that the width of the boom corresponds to the width of the lattice pieces. To increase the lateral stiffness in such a construction, larger, in particular wider, lattice pieces must therefore be used. However, this represents a substantial cost factor since completely new crane boom parts have to be purchased and/or produced for lifting heavy loads. In another respect, it is necessary for the transport of the lattice boom that the transport size does not exceed the maximum permitted transport size for road transport.
A possible solution approach is known from DE 10 2009 016 033 A1 and is shown in FIGS. 1a and 1b. The lattice boom structure has a pivotal connection piece 1 which is pivotably supported at the superstructure of a crane about a horizontal pivot axis 5. A lower cross-beam 2 is furthermore used which forms the transition from the pivotal connection piece 1 to the two-strand region 11 of the boom and ensures the flow of force through the boom. A single-strand region 10 adjoins the upper end of the two-strand region 11, with an upper cross-beam 3 likewise being used here for the flow of force. The existing light lattice pieces from the luffing fly jib of the crane are used as the lattice pieces 21 for the two-strand region. To be able to provide an optimum lifting capacity, they are assembled rotated by 90° in comparison to a use in the luffing fly jib.
As can be seen from FIG. 1a, the longitudinal axis of the bolts used at the bolt connection sites 22 extends parallel to the luffing plane, i.e. out of the plane of the drawing. It is, however, disadvantageous in this respect that, in comparison with the usual assembly of the lattice boom, the used light lattice pieces 21 are rotated by 90° and thus represent a basic problem during the assembly of the crane. DE 10 2009 016 033 A1 also proposes the use of first and second lattice pieces for the use in the single-strand and two-strand regions of the lattice mast boom.